On Wednesday, 5 September 2012 at 11:50:12 UTC, bearophile wrote:
Don Clugston:
I'd be interested to know if that idea is ever used in real
code. I mean, it's a classic trendy template toy, but does
anyone actually use it?
As usual I don't have usage statistics.
I like dynamic languages, like Python. But if you give me a
static type system, then I want something back from the
language. Detecting certain bugs at compile-time is one way to
pay me back.
If you want most programmers to use a feature like units, it
needs:
- Built-in, in the standard library, or easy to install;
- To have a compact and very nice looking syntax;
- Easy enough to use;
- Flexible, to be able to represent all units you find in many
real problems;
- Have zero or near-zero run-time costs, in both CPU and memory;
- Give acceptable error messages.
I think in F# people are using units often enough.
If a units system will be present in Phobos and it will be very
good to use, maybe D programmers will use them.
I am currently using Haskell a little, and I am enjoying giving
types to values to tell them apart in terms of their usage.
I say this because I've done a lot of physics calculation
involving multiple complicated units, but never seen a use for
this sort of thing.
In my experience, problems involving units are easily
detectable (two test cases will catch them all).
The most insidious bugs are things like when you have used
constants at 25'C instead of 20'C, or when you have a sign
wrong.
There are some famous problems caused by mixing units:
http://lamar.colostate.edu/~hillger/unit-mixups.html
Maybe this is the most famous:
http://mars.jpl.nasa.gov/msp98/news/mco990930.html
Bye,
bearophile
FWIW, there was a proposal (JSR-275) to add support for units of
measure to Java that was ultimately rejected. The implementation
can be found at JScience.org, written and maintained by the
website owner, Jean-Marie Dautelle, who also led the JSR team.
Paul
